The present invention relates to a linear motor.
Japanese Patent Laid-open publication No. 2001-286122 discloses a linear motor comprising a moving member constructed of a permanent magnet rod and a stator constructed of an armature. The permanent magnet rod has a magnetically permeable shaft and a permanent magnet row. The permanent magnet row comprises a plurality of permanent magnets which are so magnetized that each has a magnetic pole with one polarity on its entire outer circumferential surface and which are arranged on the shaft so that opposite polarities alternately appear in an axial direction of the shaft. The armature has an armature core and a plurality of excitation windings wound in a ring-like shape in a circumferential direction of the permanent magnet rod. The armature core comprises divided cores combined together to hold the excitation windings in between. Each of the divided cores has a cylindrical yoke structure forming a yoke, a cylindrical magnetic pole surface forming portion, and a ring-shaped connecting portion connecting the yoke structure and the magnetic pole surface forming portion.
In the conventional linear motors, however, since the cylindrical yoke structure must be provided, the armature core has a complicated shape. Further, the divided cores are formed by cutting a silicon iron material. This raises the manufacturing cost of the armature core and also increases a core loss due to an eddy current. The conventional linear motors have another problem of a low degree of freedom of design.
An object of the present invention is to provide a linear motor that does not require a cylindrical yoke structure.
Another object of the present invention is to provide a linear motor which has a lowered manufacturing cost of the armature core, a reduced core loss and a higher degree of freedom of design.